Ozone hole over Antarctica 'at record size'

The ozone hole over Antarctica - which exposes Southern Hemisphere countries to dangerous levels of ultraviolet (UV) radiation, which causes skin cancer - is at a near record size this spring, a New Zealand scientist said today.

Dr Stephen Wood of New Zealand's National Institute of Water and Atmospheric Research, who is in Antarctica studying the ozone hole, said it was currently about 27 million square kilometres, almost four times the size of Australia.

Wood said the skin-cancer danger for New Zealand, Australia and other Southern Hemisphere countries this summer would depend on how quickly the ozone hole begins to break up, releasing increased UV light.

He said the seasonal phenomenon had developed earlier than usual this spring but had shrunk a little after threatening to match the record 30 million square kilometres of three years ago.

Wood said that although the Antarctic ozone hole was smaller last year and broke up earlier because of unusual meteorological conditions, it did not point to an end of the problem of depleted ozone in the layer of the atmosphere about 10 km above Earth.

"What this means is that although the manmade chemicals that contribute to the ozone depletion are already starting to decline in the atmosphere, we haven't yet seen a sustained reduction in the severity of the Antarctic ozone hole," he said.

"There will always be variations from one year to the next, so before we can confirm the expected recovery, we would need to see smaller or less severe ozone holes over a number of years.

"Realistically, it might take another 10 years before we can be sure."

He told Radio New Zealand that scientists predicted "we are at the peak of the ozone-hole phenomenon and it will start to get better".

But he said the effect of other chemicals that had been brought in as replacements for those that initially caused the problem were unknown. and the impacts of climate change could delay the recovery.

The ozone hole develops over the Antarctic every August or September and usually dissipates in November.

A similar hole usually also appears each Northern Hemisphere spring over the Arctic.